1. Field of the Invention
The present invention relates to passive desiccant systems and more particularly to passive desiccant systems for use with optical systems on aircraft.
2. Brief Description of Prior Developments
Optical systems installed on high altitude flying aircraft are exposed to varying pressures and temperatures due to changing environmental conditions. In the case of partially sealed optical systems moisture can penetrate the seals and create an obscuration in the optical path as the aircraft flies to altitude and the optics are exposed to low temperatures.
A high rate of air flow shortens the life of the desiccant; necessitates a short replacement cycle; provides high moisture content under slightly degraded condition; allows excessive moisture to be injected due to high air flow; and creates condensation at high altitudes due to pressure differential between cabin and ambient air.
A need exists, therefore, for a way to keep moisture out of an optical system when systems are mounted external to the aircraft.